Printed wiring board connection structure

ABSTRACT

The present invention relates to a connection structure for a printed wiring board to be electrically connected to a FPC. The FPC comprises a long substrate, a plurality of conductors laminated on the surface of the substrate and extending along an axial direction of the substrate. The printed wiring board comprises a planar main wiring board, an insertion opening, and a plurality of the through-hole terminals. Each of the conductors of the FPC abuts the through-hole terminal upon the insertion of the FPC into the insertion opening of the printed wiring board. According to the invention, a connector structure to be connected to FPC is provided inside the printed wiring board in order to mount circuit element in high density, and thus improve degree of freedom in designing wiring pattern.

FIELD OF THE INVENTION

The present invention relates to a structure for a printed wiring board.More particularly, the present invention relates to a structure for aprinted wiring board for electrically connecting the printed wiringboard formed from laminating a plurality of board members and FPCs(Flexible Printed Circuits).

RELATED ART

Conventionally, electronic component modules and printed wiring boardsare mounted in electronic devices. FPC have been used to connect theseprinted wiring boards and electronic component modules.

The printed wiring board includes an insulating substrate, a wiringpattern which is formed on this substrate, and circuit elements, such asICs and connectors, which are connected to this wiring pattern on thesubstrate. ZIF (Zero Insertion Force)-type connectors which can beinserted and removed from FPCs with little force are connectorsincluding the circuit elements (for example, refer to Japanese PatentApplication Laid-open Publication No. 2002-158055).

According to this ZIF-type connector, operability of a FPC and a slidercan be improved and connection reliability ensured, while realizingminiaturization.

The miniaturization of electronic devices such as mobile phones andmobile devices has been progressing in recent years, and, with thisminiaturization of electronic devices, the miniaturization and highlevels of integration of FPC and printed wiring boards are also indemand. Therefore, in order to meet this demand, in recent years,multilayer printed wiring boards which stack a plurality of substrateshave come into wide use.

However, although the foregoing ZIF-type connector realizes low height,it occupies a certain area on the substrate because it is mounted on asurface of the substrate of the printed wiring board. Therefore, therewere cases that mounting circuit elements with high-density becamedifficult.

In order to solve the above problems, an object of the present inventionis to provide a structure for printed wiring boards wherein circuitelements can be mounted with high-density.

SUMMARY OF THE INVENTION

The inventors have invented a structure for printed wiring boards tosolve the problems mentioned above as follows.

(1) A connection structure for a printed wiring board to be electricallyconnected to a FPC, the FPC including: a long substrate, a plurality ofconductors laminated on a surface of the substrate and extending alongan axial direction of the substrate; the printed wiring boardincluding-: a planar main wiring board, an insertion opening provided atan edge surface of the main wiring board and inserted by an end portionof the FPC, and a plurality of the through-hole terminals penetratingfrom a surface of the main wiring board through an internal wall surfaceof the insertion opening, the conductor of the FPC abutting eachthrough-hole terminal upon insertion of said FPC into the insertionopening of the printed wiring board.

The FPC may be a FFC (Flexible Flat Cable).

The substrate may be formed of, for-example, a thin film polyimideplate. The substrate may also be laminated with a reinforced plate.

The conductor may be formed of a suitable material having conductivityand formability, such as, for example, a copper alloy plate. Theconductor may be plated with nickel or may be treated with conductivehard plating. A base end of the conductor may be coated with a polyimidefilm.

The conductor may be formed by being laminated (adhered) to the longsubstrate and etched thereafter. Each of the conductors may be connectedto a low voltage power supply or a ground.

Vias, pads-on-holes, and so on, other than the through-hole terminal,may be formed on the printed wiring board. Alternatively, insulatingsubstrates and conductor layers formed on the substrate surface may belaminated on the main wiring board of the printed wiring board. Thesesubstrates and conductor layers may be integrated by way of through-holeplating.

The location of the through-hole terminal is not limited but may beappropriately selected corresponding to the location of the FPCconductors. A hole diameter of the through-hole terminal may also beappropriately selected.

According to the invention as described in (1), the connector structureto be connected to FPC is provided inside the printed wiring board inorder to mount circuit elements at high density, and thus improve adegree of freedom in designing wiring patterns.

Existing FPC flat conductors can be utilized without any changes andthus reduction of manufacturing cost of the FPC can be achieved.

(2) In the connection structure for the printed wiring board accordingto (1), the conductor of the FPC is welded to the through-hole terminalby filling a molten solder in the through-hole terminal.

(3) In the connection structure for the printed wiring board accordingto (1), a press fit pin is pressed in the through-hole terminal.

According to the invention described in (3), the insertion of the pressfit pin into the through-hole terminal electrically connects thethrough-hole terminal and the FPC conductor through the press fit pin.

(4) In the connection structure for the printed wiring board accordingto (3), the press fit pin includes a main body accommodated in thethrough-hole terminal, an abutting portion provided on one end side ofthe main body and penetrating from an internal wall surface of theinsertion opening, a circular-shaped flange provided on other end of themain body and exposed to the surface of the printed wiring board.

The shape of the abutting portion of the press fit pin may be of aplanar, curved, or spherical shape.

The shape of the main body of the press fit pin is not limited inparticular. The main body may be formed in a shape of a rectangularcolumn, for example, a square pole, so that the main body is secured topress an internal circumferential surface of the through-hole terminal.Alternatively, the main body of the press fit pin may be a cylindricalcolumn having an external diameter slightly larger than the internaldiameter of the through-hole terminal, and is formed by breaking at anotch along a length of the main body so that the main body can pressthe internal circumferential surface of the through-hole terminal.

The flange of the press fit pin may have an external diametercorresponding to a front layer land diameter of the through-holeterminal. The flange may be attached to the through-hole terminal bymeans of soldering.

According to the invention described in (4), the abutting portion of thepress fit pin abuts the conductor of a FPC so that the conductor of theFPC and the through-hole terminal can be electrically connected.

(5) In the connection structure for the printed wiring board accordingto any one of (1) to (4), the main wiring board of the printed wiringboard is formed by laminating a first external layer plate, an internalplate having a notch formed at an edge surface, and a second externallayer, the through-hole terminal formed on the first external layerplate, the insertion opening formed by having therearound the firstexternal layer plate, the notch in the internal plate, and the secondexternal layer.

The width of the notch may be slightly larger than the width of FPC. Thenotch can thus control a dislocation of the FPC in a direction of width,allowing an easy alignment of the FPC conductor and the through-holeterminal.

The aforementioned second external layer plate, the internal plate, thefirst external layer plate and a prepreg as will be discussed later aretypically made of an epoxy resin. In addition, these plates and theprepreg may be formed of a material which is not limited to the epoxyresin, but materials having a heat resistance such as a BT resin, etc.,may also be used. Furthermore, these plates and the prepreg may beformed of such materials having low dielectric constant properties aslow dielectric constant epoxy resins, and polyphenylene ether resins.

A plate thickness of the internal plate is preferably 0.2 mm to 1.6 mm,and more preferably 0.6 mm to 1.0 mm.

The plate thickness of the first external layer plate, the secondexternal layer plate is preferably 0.2 mm. The thickness of a copperfoil is preferably 35 micrometers.

(6) In the connection structure for the printed wiring board accordingto (5), the first external layer plate and the second external layerhave wiring patterns formed on both surfaces thereof and further havethe prepreg and a copper foil laminated thereon and integrated by way ofsolder plating.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view showing a FPC and a printed wiring boardaccording to a first embodiment of the present invention.

FIG. 2 is an exploded perspective view of a printed wiring boardaccording to the aforementioned embodiment.

FIG. 3 is a cross-sectional view of a FPC according to aforementionedembodiment inserted in the printed wiring board.

FIG. 4 is a perspective view showing a FPC and a printed wiring boardaccording to a second embodiment of the present invention.

FIG. 5 is a cross-sectional view of a FPC inserted in the printed wiringboard according to the aforementioned embodiment.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

With reference to drawings, each embodiment of the present inventionwill be described hereinafter in detail. In the description of theembodiments below, identical components are given identical referencenumerals and explanation is omitted or simplified for the sake ofbrevity.

First Embodiment

FIG. 1 is a perspective view showing a FPC 2 and a printed wiring board1 according to a first embodiment of the present invention.

FPC 2 includes a long substrate 22, a reinforcing plate 23 bonded to thelower surface of the substrate 22, a plurality of conductors 21laminated on the upper surface of the substrate 22 and extending alongan axial direction thereof.

FPC 2 is coated with a polyimide film 25 with an end side is exposed toform an exposed conductor 2A.

The substrate 22 has an insulation property and is formed, for example,of a thin-film polyimide plate.

The exposed conductor 2A has a width W2.

FIG. 2 is an exploded perspective view of the printed wiring board 1.

The printed wiring board 1 includes a planar main wiring board 13, aninsertion opening 10B provided at an edge surface of the main wiringboard 13 so as to have the end portion of the FPC 2 inserted therein,and a plurality of the through-hole terminals 11A penetrating from thesurface of the main wiring board 13 through the internal wall surface ofthe insertion opening 10B.

Here, the main wiring board 13 is configured with a first external layerplate 11, an internal plate 10, and a second external layer plate 12laminated in this order.

The internal plate 10 is formed of an insulating plate member, or anepoxy glass plate in this embodiment. The internal plate 10 has a platethickness T0, and has a notch to the edge surface 10A with a width W1and a depth D.

The first external layer plate 11 has a plate thickness T1, that is 0.2mm in this embodiment. On both surfaces of the first external layerplate 11, copper foil is print-etched to provide wiring patterns 11B.Specifically, the thickness of the copper foil is 35 micrometers.

The first external layer plate 11 is provided with a plurality ofthrough-hole terminals 11A penetrating through the front and backsurface of the plate. These through-hole terminals 11A are arranged in arow such that each terminal intersects the insertion direction of FPC 2and is connected to the wiring patterns 11B.

The second external layer plate 12 has a plate thickness T2, which is0.2 mm in this embodiment. On both surfaces of the second external layerplate 12, the copper foil is print-etched to provide wiring patterns.Specifically, the thickness of the copper foil is 35 micrometers.

The printed wiring board 1 is manufactured by following steps.

Specifically, the first external layer plate 11, the internal layerplate 10, and the second external layer 12 are laminated and pressed inthis order and integrated by solder plating. The integrated platemembers 10 to 12 are formed with through-hole terminals, vias,Pads-on-holes etc., and are then subjected to soldering and resistprocessing.

The first external layer plate 11, the notch 10A of internal plate 10,and the second external layer 12 are provided on the edge surface of theprinted wiring board 1 and forms the insertion opening 10B in which theend portion of FPC 2 is inserted.

The plurality of through-hole terminals 11A described above penetratefrom the surface of the printed wiring board 1 to the internal wallsurface of the insertion opening 10B.

The width W1 of the notch 10A is slightly larger than the width W2 ofFPC 2. The notch 10A can thereby limit a displacement of FPC 2 in thewidth direction, allowing an easy alignment of the conductor 21 of theFPC 2 and the through-hole terminals 11A of the printed wiring board 1.

With reference to FIG. 3, a process of the inserting FPC 2 into theprinted wiring board 1 will be described.

When the end portion of the FPC 2 is inserted into the insertion opening10B of the printed wiring board 1, the conductor 21 of the FPC 2 abutsthe through-hole terminal 11A. Then, pouring molten solder into thethrough-hole terminal 1A welds the through-hole terminal 11A andconductor 21 of FPC 2. This electrically connects the printed wiringboard 1 and FPC 2.

Second Embodiment

This embodiment differs from the first embodiment in that the press fitpin 3 is pressed into a through-hole terminal 11A.

FIG. 4 is a perspective view showing a FPC 2 and a printed wiring board1A according to the second embodiment of the present invention.

The press fit pin 3 is pressed into the through-hole terminal 11A. Thepress fit pin 3 comprises a main body 32 accommodated in thethrough-hole terminal 11A, an abutting portion 31 provided on one end ofthe main body 32 and projects from the internal wall surface of theinsertion opening 10B, a circular-shaped flange 33 provided on other endof the main body 32 and exposed to the surface of the printed wiringboard 1.

The abutting portion 31 abuts the conductor 21 of FPC 2. The abuttingportion 31 is of a circular shape.

The main body 32 is formed in the shape of a square pole. The distancebetween a side and an opposing side on a diagonal line of the squarepole is formed slightly wider than the internal diameter of thethrough-hole terminal 11A.

The flange 33 has an external diameter corresponding to a surface landdiameter of the through-hole terminal 11A.

With reference to FIG. 5, a process of inserting FPC 2 into the printedwiring board 1 will is described.

When the end portion of the FPC 2 is inserted to the insertion opening10B of the printed wiring board 1A, the conductor 21 of the FPC 2 abutsthe abutting portion 31 of the press fit pin 3. This electricallyconnects the printed wiring board 1A and FPC 2.

According to the present invention, the following advantageous effectsare provided.

A connector structure to be connected to FPC is provided inside theprinted wiring board in order to mount a circuit element at highdensity, and thus improve a degree of freedom in designing wiringpattern.

Existing FPC flat conductors can be utilized without any changes andthus reduction of manufacturing cost of the FPC can be achieved.

1. A connection structure for a printed wiring board to be electricallyconnected to a FPC; the FPC comprising: a long substrate, a plurality ofconductors laminated on a surface of said substrate and extending alongan axial direction of the substrate; said printed wiring boardcomprising: a planar main wiring board, an insertion opening provided atan edge surface of the main wiring board and inserted by an end portionof said FPC, and a plurality of the through-hole terminals penetratingfrom a surface of said main wiring board through an internal wallsurface of said insertion opening, a conductor of the FPC abutting eachthrough-hole terminal upon insertion of said FPC into the insertionopening of said printed wiring board.
 2. The connection structure forthe printed wiring board according to claim 1, the conductor of said FPCwelded to said through-hole terminal by filling a molten solder in saidthrough-hole terminal.
 3. The connection structure for the printedwiring board according to claim 1, a press fit pin is pressed in saidthrough-hole terminal.
 4. The connection structure for the printedwiring board according to claim 3, said press fit pin comprises a mainbody accommodated in said through-hole terminal, an abutting portionprovided on one end side of said main body and penetrating from aninternal wall surface of said insertion opening, a circular-shapedflange provided on other end of said main body and exposed to thesurface of said printed wiring board.
 5. The connection structure forthe printed wiring board according to claim 1, said main wiring board ofsaid printed wiring board is formed by laminating a first external layerplate, an internal plate having a notch formed to an edge surface, and asecond external layer, said through-hole terminal formed on said firstexternal layer plate, said insertion opening formed by havingtherearound said first external layer plate, the notch in said internalplate, and the second external layer.
 6. The connection structure forthe printed wiring board according to claim 2, said main wiring board ofsaid printed wiring board is formed by laminating a first external layerplate, an internal plate having a notch formed to an edge surface, and asecond external layer, said through-hole terminal formed on said firstexternal layer plate, said insertion opening formed by havingtherearound said first external layer plate, the notch in said internalplate, and the second external layer.
 7. The connection structure forthe printed wiring board according to claim 3, said main wiring board ofsaid printed wiring board is formed by laminating a first external layerplate, an internal plate having a notch formed to an edge surface, and asecond external layer, said through-hole terminal formed on said firstexternal layer plate, said insertion opening formed by havingtherearound said first external layer plate, the notch in said internalplate, and the second external layer.
 8. The connection structure forthe printed wiring board according to claim 4, said main wiring board ofsaid printed wiring board is formed by laminating a first external layerplate, an internal plate having a notch formed to an edge surface, and asecond external layer, said through-hole terminal formed on said firstexternal layer plate, said insertion opening formed by havingtherearound said first external layer plate, the notch in said internalplate, and the second external layer.
 9. The connection structure forthe printed wiring board according to claim 5, said first external layerplate and said second external layer having wiring patterns formed onboth surfaces thereof and further having a prepreg and a copper foillaminated thereon and integrated by way of solder plating.
 10. Theconnection structure for the printed wiring board according to claim 6,said first external layer plate and said second external layer havingwiring patterns formed on both surfaces thereof and further having aprepreg and a copper foil laminated thereon and integrated by way ofsolder plating.
 11. The connection structure for the printed wiringboard according to claim 7, said first external layer plate and saidsecond external layer having wiring patterns formed on both surfacesthereof and further having a prepreg and a copper foil laminated thereonand integrated by way of solder plating.
 12. The connection structurefor the printed wiring board according to claim 8, said first externallayer plate and said second external layer having wiring patterns formedon both surfaces thereof and further having a prepreg and a copper foillaminated thereon and integrated by way of solder plating.